Fuel control diagnostic systems and methods

Abstract

A fault diagnostic system of a vehicle includes an error module, a proportional integral (PI) module, and a fault module. The error module determines an error based on a difference between a sample of a signal generated by an exhaust gas oxygen sensor and a target value of the sample. The PI module determines a proportional correction based on the error, determines an integral correction based on the error, and determines a fueling correction based on the proportional and integral corrections. The fault module selectively diagnoses a fault based on the integral correction and the fueling correction.

What is claimed is:  
     
       1. A fault diagnostic system of a vehicle, comprising:
 an error module configured to determine an error based on a difference between a sample of a signal generated by an exhaust gas oxygen sensor and a target value of the sample; 
 a proportional integral (PI) module configured to determine: (i) a proportional correction based on the error; and (ii) an integral correction based on the error, and further configured to determine a fueling correction based on the proportional and integral corrections; and 
 a fault module configured to diagnose a fault based on the integral correction and the fueling correction and to illuminate a malfunction indicator lamp (MIL) when the fault is diagnosed. 
 
     
     
       2. The fault diagnostic system of  claim 1  further comprising an equivalence ratio (EQR) module configured to control fueling of an engine based on the fueling correction. 
     
     
       3. The fault diagnostic system of  claim 2  wherein the EQR module is configured to control the fueling of the engine based on a sum of the fueling correction and a requested EQR. 
     
     
       4. The fault diagnostic system of  claim 1  wherein:
 the PI module is further configured to limit the integral correction to a first predetermined maximum value and is further configured to limit the proportional correction to a second predetermined maximum value; and 
 the fault module is configured to diagnose the fault further based on the first and second predetermined maximum values. 
 
     
     
       5. The fault diagnostic system of  claim 4  further comprising:
 a first averaging module configured to determine a first average of values of the integral correction determined during a period; and 
 a second averaging module configured to determine a second average of values of the fueling correction determined during the period, 
 wherein the fault module is configured to diagnose the fault based on the first and second average values and the first and second predetermined maximum values. 
 
     
     
       6. The fault diagnostic system of  claim 5  further comprising:
 a first normalizing module configured to determine a first normalized value based on the first average and the first predetermined maximum value; and 
 a second normalizing module configured to determine a second normalized value based on the second average and the second predetermined maximum value, 
 wherein the fault module is configured to diagnose the fault based on the first and second normalized values. 
 
     
     
       7. The fault diagnostic system of  claim 6  wherein the fault module is configured to indicate that the fault is present when at least one of:
 the first normalized value is greater than a first predetermined fault value; and 
 the second normalized value is greater than a second predetermined fault value. 
 
     
     
       8. The fault diagnostic system of  claim 6  wherein the fault module is configured to indicate that the fault is not present when at least one of:
 the first normalized value is less than a first predetermined fault value; and 
 the second normalized value is less than a second predetermined fault value. 
 
     
     
       9. The fault diagnostic system of  claim 6  wherein:
 the first normalizing module is configured to set the first normalized value based on the first average divided by the first predetermined maximum value; and 
 the second normalizing module is configured to set the second normalized value based on the second average divided by the second predetermined maximum value. 
 
     
     
       10. A fault diagnostic method for a vehicle, comprising:
 generating, using an exhaust gas oxygen sensor, a signal based on oxygen in exhaust output by an engine; 
 determining, using an engine control module (ECM), an error based on a difference between a sample of the signal generated by the exhaust gas oxygen sensor and a target value of the sample; 
 determining, using the ECM, a proportional correction based on the error; 
 determining, using the ECM, an integral correction based on the error; 
 determining, using the ECM, a fueling correction based on the proportional and integral corrections; 
 using the ECM, indicating that a fault is present based on the integral correction and the fueling correction; and 
 using the ECM, illuminating a malfunction indicator lamp (MIL) when the fault is present. 
 
     
     
       11. The fault diagnostic method of  claim 10  further comprising controlling fueling of the engine based on the fueling correction. 
     
     
       12. The fault diagnostic method of  claim 11  further comprising controlling the fueling of the engine based on a sum of the fueling correction and a requested equivalence ratio (EQR). 
     
     
       13. The fault diagnostic method of  claim 10  further comprising:
 limiting the integral correction to a first predetermined maximum value; 
 limiting the proportional correction to a second predetermined maximum value; and 
 diagnosing the fault further based on the first and second predetermined maximum values. 
 
     
     
       14. The fault diagnostic method of  claim 13  further comprising:
 determining a first average of values of the integral correction determined during a period; 
 determining a second average of values of the fueling correction determined during the period; and 
 diagnosing the fault based on the first and second average values and the first and second predetermined maximum values. 
 
     
     
       15. The fault diagnostic method of  claim 14  further comprising:
 determining a first normalized value based on the first average and the first predetermined maximum value; 
 determining a second normalized value based on the second average and the second predetermined maximum value; and 
 diagnosing the fault based on the first and second normalized values. 
 
     
     
       16. The fault diagnostic method of  claim 15  further comprising indicating that the fault is present when at least one of:
 the first normalized value is greater than a first predetermined fault value; and 
 the second normalized value is greater than a second predetermined fault value. 
 
     
     
       17. The fault diagnostic method of  claim 15  further comprising indicating that the fault is not present when at least one of:
 the first normalized value is less than a first predetermined fault value; and 
 the second normalized value is less than a second predetermined fault value. 
 
     
     
       18. The fault diagnostic method of  claim 15  further comprising:
 setting the first normalized value based on the first average divided by the first predetermined maximum value; and 
 setting the second normalized value based on the second average divided by the second predetermined maximum value.